1. Technical Field
The present invention relates to a technology for supplying a low-ripple voltage to a load.
2. Related Art
Portable electronic apparatuses, which are required to be thin and lightweight, include displays using electro-optical devices, such as liquid-crystal devices and organic-electroluminescent (EL) devices, that can meet such requirements. Since a voltage required for driving an electro-optical device is higher than a voltage of 3 to 5 V for activating a logic of an electronic apparatus, a power-supply circuit is required for the electronic apparatus to boost a single direct-current voltage of a battery or the like.
A variety of power-supply circuits of this type are available. In a portable electronic apparatus for which compactness, simplicity, low power consumption, and the like are required, a power-supply circuit is generally configured such that a voltage generated by turning on and off (switching) is held in a capacitor (holding device) provided at an output stage while being smoothed and supplied to a load (see, for example, Japanese Unexamined Patent Application Publication No. 2000-278938 and Japanese Unexamined Patent Application Publication No. 2001-117649).
Although the capacitor is provided at the output stage of the power-supply circuit, some ripples appear since the voltage across the capacitor is increased by switching while being gradually attenuated with power consumption by a load. It is desired that such ripples be minimized because they cause fluctuations in the root-mean-square (rms) value of a voltage applied to the electro-optical device and affect the quality of display.
The present invention has been made in view of the circumstances described above, and its object is to provide a voltage-supply circuit, a voltage-supply method, a power-supply circuit, an electro-optical unit, and an electronic apparatus that can supply a low-ripple voltage.